1. Technical Field
This invention relates generally to electrochemical cell construction, and more particularly to an electrochemical cell having a singular external coupling.
2. Background Art
Portable electronic devices are becoming more and more popular. Many people today use multiple portable electronic devices daily. These devices include mobile telephones, personal digital assistants, portable music players, cameras, calculators, watches, radios, and computers, just to name a few. These portable devices derive their portability from batteries. Batteries, including rechargeable batteries, allow portable devices to slip the surly bonds of wall outlets and touch the face of a world on the move.
Each battery, be it rechargeable or primary, relies on an electrochemical cell for energy storage. While there may be other components in the battery pack, including circuit boards, mechanical assemblies, protection components, charging components, fuel gauging circuits, temperature measurement circuits and indicator circuits, energy is stored and released by the electrochemical cell.
Each electrochemical cell includes a cathode and an anode. The two are electrically isolated, and offer a current path into or away from the electrochemical cell. Turning now to FIG. 1, illustrated therein is a prior art rechargeable cell 100. In such a rechargeable cell 100, the anode and cathode are electrically isolated by a separator. The anode-separator-cathode assembly 101 is then either wound in a “jellyroll” configuration or laminated in a stack.
An anode conductive tab 102 and a cathode conductive tab 103 are coupled to the anode and cathode, respectively. Each tab 102,103, generally constructed from metal foil, is then joined to an external tab 104,105. The external tabs 104,105 provide electrical conductivity to external components. As with the anode and cathode, the conductive tabs 102,103 and the external tabs 102,103 must remain electrically isolated from each other.
To accomplish the electrical isolation, the cell assembly is placed in an enclosure 106. The opening 107 of the enclosure 106 is then sealed about the external tabs 104,105. A tight seal is required about the external tabs 104,105 to prevent any electrolyte from escaping the enclosure 106. The tight seal also prevents dust, moisture, and debris from entering the cell.
To ensure a tight seal, with no space or pockets on the sides of the external tabs 104,105, plastic sealing members 108,109 are placed about the external tabs 104,105. The enclosure 106 is then sealed about the plastic sealing members 108,109.
The prior art configuration of FIG. 1 works well as long as the width 110 of the cell structure 101 is sufficient to accommodate two external tabs, associated components, and a corresponding mechanical seal. When the width 110 of the cell structure 101 becomes smaller, the external tabs 104,105 get closer and closer together. This can compromise reliability, as the external tabs 104,105—when too close—can short the anode and cathode. Further, the quality of the manufacturing process used to construct the cell can be adversely affected when the external tabs 104,105 get too close together.
There is thus a need for an improved cell interconnect that accommodates narrow electrochemical cells.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.